I generally don't check in or enter on the ground level at PHL (though it's one of my home airports), but in the future I'm just going to switch into Russian and act like I have no idea what saying, then accuse them of theft when they try to grab my bag, and call for the police in broken English.

J/k, I don't have the guts for that. But I am of the opinion that the bottom of the escalator, and by contract employees without a mandate clear to passengers, is not the way to go about addressing this problem.